Abathur was created by the Overmind as a "brood of one", spun from many species.[3][4] While it was the Overmind that was the will of the zerg's drive to perfect, it was Abathur who was the instrument of its will.[5]

By the Overmind's instruction he designed the Queen of Blades by wrapping her in a chrysalis, though not without injuring her in the process.[3][6]

"What did you do after the Overmind died?""Wandered the tunnels of Char, without purpose. Feral. Queen of Blades found me. Made me zerg again.""You aren't zerg unless you are under someone's control?""Without overriding will, am beast. Less."

After the Overmind's death, Abathur became feral and purposeless. He wandered under Char, eating whatever tried to attack him.[7] He modified any zerg he came across, and grew fixated on diversifying the Swarm.[5] The Queen of Blades retrieved him and took him under her command.[3][4] He was responsible for the development of new queens, removing their ability to fly in order to improve their abilities to care of the hive.[8] Kerrigan also gave him terrans to experiment on.[3][9]

Kerrigan, now following her own agenda, found Abathur aboard a leviathan. To her frustration, Abathur seemed to consider her and the Queen of Blades as separate entities. In Abathur's view, the Queen of Blades had carried ancient zerg qualities, with only minor terran influence. Kerrigan as she was now, was "infected" with more terran matter. He offered to 'improve' Kerrigan but she refused. She was, however, willing to let Abathur evolve the Swarm. She was suffering from memory loss, and could not recall her background with the creature.

Abathur obliged. While Kerrigan was out on missions, Abathur experimented on zerg and searched for worlds where he could derive strains from existing breeds. When readied, he showed these to Kerrigan through demonstrations, and evolved the appropriate strain chosen by her.[11] Kerrigan eventually learnt the truth of what Abathur had done to her after her infestation at Tarsonis. She told him that she'd have killed him if he wasn't vital to her plans. Abathur was puzzled by her anger.[3]

Kerrigan brought her Swarm to the icy moon of Kaldir. Abathur commented that the zerg were suffering due to the moon's extreme cold, with temperatures as low as that of deep space. He explained that apart from the leviathan and Mutalisks, there was no need to have driven the Swarm to adapt to such cold temperatures beforehand. He informed Kerrigan that he would look for local fauna, to assimilate their essence to allow the zerg to better cope with the conditions.[3][12] He recommended that the Swarm absorb ursadon matriarch essence to achieve this end.[13]

In the conflict that resulted against the protoss forces present on the moon, a prisoner was taken at Abathur's request. He wanted to dissect her, even though protoss genetic material was useless to the Swarm. Instead, Kerrigan kept the protoss as a prisoner.[14][15]

In the subsequent battle, Abathur was able to reconstruct the hydralisk. He recommended that Kerrigan's forces retrieve biomass the protoss had stored.[16] The protoss forces on the ground were defeated, but they still had a spaceworthy vessel that they intended to escape to Shakuras. By implanting the prisoner with a parasite and letting the protoss teleport her away, Kerrigan was able to use the parasite (which turned into a queen) to cripple the protoss ship from the inside.[17] Abathur was impressed with Kerrigan's lateral thinking, but did not know the parasite's origins. Kerrigan revealed that she had created it herself, that Abathur wasn't the only one able to spin sequences. Taking in the "revelation," Abathur continued his work.[3][18]

On Char, Dominion and Swarm forces were vying for control of the planet, led by General Horace Warfield and Broodmother Zagara respectively. Kerrigan brought Zagara into the fold[19] and sent her to Abathur so that he could improve the broodmother's cognitive abilities.[20][9] She also instructed Abathur to cease experiments on terrans, something that he was glad to hear due to their lack of biological worth to the Swarm.[3][19]

The Swarm moved on Warfield through the Bone Trench. Abathur advised her on the location of valuable zerg biomass. The attack was successful, and the Dominion forces retreated.[21]

The Swarm assaulted Warfield's compound. Zagara presented Kerrigan with some aberrations to use in the battle. Abathur commented that their sequences were "sloppy, yet, effective." They were put to good use, and the Dominion was driven off Char.[22]

"Primal zerg. Unacceptable. Must be wiped clean. No trace left. Destroy primal zerg.""What are you talking about?""Saw ranged primal zerg creatures on battlefield!? Based on hydralisk! Primal zerg stole design from Swarm! Swarm on planet for hours, days, already being replicated!""Abathur, are you upset?""Unacceptable! Swarm's power, ability to assimilate strengths. Primal zerg must not take from us!""Don't worry about it. They'll be on our side before I am done here."

Kerrigan took the Swarm to Zerus, the homeworld of the zerg. There, they encountered the primal zerg, those who had escaped control of the Overmind. Abathur had mixed feelings about them, but reasoned that there might be some good essence to take from them.[3][23] In the battle that followed, Abathur provided Kerrigan with newly reconstituted mutalisks to use against their foes' primal guardians. He also directed her to primal essence pools, and recommended the destruction of the primal hive.[24]

After the battle, Abathur's view on the primal zerg soured. They'd adapted Swarm essence into their own physiology within hours, days at the most. He wanted to destroy them, but Kerrigan reassured him that they'd be brought into the fold.[3][25] On that note, Abathur presented her with his latest creation, the swarm host. They were used to defend Kerrigan from the primals as she entered the first spawning pool. The defensive action was successful, and Kerrigan emerged, now the Primal Queen of Blades.[26]

Kerrigan returned to the leviathan. Abathur noted that Kerrigan's genetic strands had been restructured from the base up. She was stronger than the old Queen of Blades, and her sequences were "clean," completely different at the core. He wanted to take a sample, but Kerrigan refused, claiming that she was beyond his comprehension. Abathur admitted she was correct—her new genetic structure was beyond his understanding.[3][27]

As Kerrigan brought the primal pack leaders into the fold, he advised Kerrigan on her new abilities, and pointed out the existence of xel'naga relics, which housed genetic information. True to her word, through the defeat of the pack leaders, Kerrigan brought the primal zerg into the Swarm.[28] Afterwards, Abathur suggested that the Swarm never return to Zerus. It was their homeworld, and the path of evolution was forward, not backwards. That, and he still preferred the Swarm zerg to their primal counterparts.[3][29]

At Skygeirr Platform, Kerrigan encountered Alexei Stukov, an infested terran who sought the destruction of the facility, which was being used to breed protoss/zerg hybrids. Kerrigan agreed.[30] Abathur found Stukov fascinating, but was disturbed by the implications—the interweaving of zerg and terran matter within him was subtle, on a scale not possible within the Swarm. He recommended that Kerrigan bring the Swarm into the fold of this entity, as it was untennable to oppose them. Kerrigan refused. That, and she suspected that Abathur was simply jealous.[3][30] He later reflected that it was implausible that it was the terrans themselves who possessed the required knowledge for this kind of genetic engineering.[31][3] Regardless, the facility was destroyed, and the Swarm departed.[32][33][34]

Kerrigan searched for the location of Jim Raynor, a terran she had a personal connection to. He was being held captive by the Dominion. Abathur explained that the zerg couldn't hack the Dominion's network due to zerg biology and terran technology being incompatible.[3][35] Still, with the help of Raynor's forces, the terran was rescued.[36][37]

Kerrigan moved on Korhal, but she needed a weapon to destroy its orbital defenses. Abathur proposed modifying the virophage gene sequence into a new weapon. He assured Kerrigan that he could develop it in time for the invasion.[3][38] The result was the bile launcher, with the new structure being deployed through sacs. On the ground, Kerrigan guarded the drop sites from Dominion forces, and a beachhead was established.[39]

While the assault was going on, Abathur directed Kerrigan to Metis, a research laboratory where the Dominion was experimenting on ultralisks. Kerrigan was able to take control of one of the creatures and overrun it from the inside. The Dominion released a toxic compound, but it was incorporated into the ultralisks, producing the noxious strain. Elsewhere, the Swarm moved against a supply center on the outskirts of Augustgrad, one that possessed experimental nuclear missiles. The nukes were fired, but mutated the attacking ultralisks into torrasques. The facility was destroyed.[40]

Prior to Kerrigan's final assault on Mengsk's palace, Abathur complimented Kerrigan as the Swarm's greatest leader. Taken aback, Kerrigan questioned Abathur's reasoning, admitting that everything she'd done had been for her own personal gain. Abathur reassured her, declaring that her reasons were irrelevant, as it was the Swarm's purpose to serve its leader, regardless of that leader's goals.[3][41]

Some time after the End War, under the direction of Zagara, now Overqueen of the zerg, the Swarm retrieved a sample of xel'naga essence from Ulnar. The samples were unable to be spun directly into zerg broods due to being too advanced for zerg DNA, but were spun into the a native, peaceful species independent of the swarm, creating the adostra. Zagara intended for the adostra to seed planets with life using their xel'naga abilities, a new direction for the Swarm. However, Abathur secretly protested the truce between races, as in his eyes war was necessary to drive the Swarm's evolution and assimilation of other races. He secretly created a second race using the xel'naga essence, the chitha, which were also independent of the Swarm but could still be commanded and controlled with vocal commands. With the aid of Mukav, a modified broodmother, Abathur plotted to instigate another war between the species to spur further zerg conquest and evolution.

When Valerian Mengsk and Artanis came to Gystt to observe Zagara's work, Abathur and Mukav directed the chitha to attack Valerian's surveying team sent to scout the planet, both on their own and by commanding other zerg. The existence of the creatures was unknown to Zagara, who denied involvement in the attacks. Abathur's hope was that the attacks would ruin any chance of peace and spark another war. However, after engaging his chitha and their controlled broods in a conflict later known as the One-Day War, his actions were eventually discovered by the three parties and he revealed his motives to Zagara. Abathur attacked Zagara and her allies with Mukav several chitha, but with the aid of protoss and terran warriors, they were all eradicated, and Zagara subdued Abathur but kept him alive to serve the Swarm under a closer watch.[44]

In Heart of the Swarm, Abathur performs a role similar to what Rory Swann and Egon Stetmann did in Wings of Liberty, upgrading and evolving zerg strains for better use in game. However, it is different from the terran system, which required a certain amount of credits collected after completed missions; instead, Abathur demands essence, acquired from completing secondary objectives in-game, to perform upgrades and evolutions.[7] In the release, evolving and upgrading zerg was at no cost, although some missions would involve Abathur requiring essence for unit upgrades or extra levels.

"Super intelligent biologist, an evolutionary craftsman. Arrogant and impatient, he wants to eat anything strange or different so that he can absorb and understand it. He sees other beings in terms of their genetic material, not as sentient beings."

Abathur is well mannered and is constantly connecting DNA, experimenting on strains and studying the Swarm's enemies.[10] He does this by eating (parts of) creatures and gaining access to their genetic code.[45] It is a process that he enjoys—even though protoss essence is incompatible with the zerg, that doesn't stop him from trying anyway.[14][15] He dislikes being in space for extended periods due to the lack of bio-matter.[3][46]

Abathur accepts that true perfection is impossible for the zerg to achieve. However, it makes sense on the tactical level for him for the zerg to continue chasing perfection regardless.[47] He also believes it is "purpose" which makes the zerg what they are. He states that without an overriding will, they are no more than beasts, much like he was after the death of the Overmind. To this end, he is grateful that the Swarm has a purpose, even if it is to fulfill Kerrigan's vendetta.[3] As much as a hive creature can, Abathur sees himself as being personally responsible for the continuation of the zerg. He undertakes each experiment as though the survival of the species depends on it alone, and tolerates no evolutionary backstep.[5]

Abathur

Abathur is unimpressed with terran essence and DNA,[47] along with their "primitive structures" and minimal biological adaptability.[3][9] He considers them to be a doomed species due to their lack of genetic diversity and proliferation of recessive traits in their gene pool.[3][48] Similarly, he holds the primal zerg in low regard, noting that though some displayed favorable traits, they were sloppy and inefficient. He thought even less of them when he discovered they quickly replicated some strains from the Swarm, prompting him to implore Kerrigan to wipe them all out. An amused Kerrigan noted that Abathur sounded upset, indicating he may hold some level of pride or possessiveness towards his "work."[3][25] Also despite his view on terrans, he is fascinated by Alexei Stukov with modifications at levels Abathur himself is unable to achieve and considers Stukov second only to Kerrigan.[3][49]

Abathur seems to be obsessed with efficiency. His goal is not to make the zerg perfect, since perfection is impossible, instead, he tries to make them as efficient as possible.[3] Outside of that, he points out to Kerrigan that killing a creature before consuming its biomass, while it would be less painful for the creature, is inefficient, since the creature's death is imminent.[3][14] He considers himself to be the most useful part of the Swarm.[3][48]

Abathur has an odd speech pattern, often leaving out conjoining words and ignoring pronouns.[3] In a way, he speaks in the most efficient manner possible, befitting his approach towards genetics.

Abathur has been noted to be a popular character within the fanbase. Allen Dilling has speculated that his popularity stems from his design, along with his manipulative nature, that the fanbase tends to gravitate towards "evil" characters.[51]

The concept of Abathur was pitched by Samwise Didier. He wanted something "spidery and spindly," with an "evil and diabolic" nature. His concept image involved Abathur using webs and the like to view the genetic structure of a creature that it was working on.[2]

At a panel at BlizzCon 2011, it was said that Abathur had his own storyline with much going on with the character. By interacting with him across the campaign, a subplot was said to be revealed that has its own climax.[52] In an earlier version of Heart of the Swarm Kerrigan would let Abathur unknowingly spin the strands and sequences of his own replacement. This successor would kill Abathur and take his place, fulfilling the subplot and Kerrigan's revenge against the original Abathur.[53]

In a preview, Abathur was hinted at having ulterior motives.[54] However, this did not make an appearance in-game.[55]

In early screenshots of Heart of the Swarm, Abathur was depicted as being present in the maw of Kerrigan's leviathan.[56] In the final version, he remained within the evolution pit.[55]

Map editor files include a duplicate Abathur actor named "Ssassan." The description of the character implies this may have been Abathur's name in a previous version of the game.[53]